1. Field of the Invention
This invention relates generally to optical spectrometer and more specifically to an optical spectrometer on mobile computing device that simultaneously self-referencing and measuring an optical spectrum of a physical object through a shared aperture as optical inputs.
2. Description of the Prior Art
Mobile computing device, especially smartphone, typically has advanced features integrated beyond making voice calls. With the integration of SoC, system-on-a-chip, high resolution camera, internet connection capability, touch-screen display, data storage capability, smartphone is able to provide extensive user-friendly services. Affordable smartphone peripheral device can enable the smartphone with a built-in camera to sense wavelength information. For example, Breslauer et al., Plos One, vol. 4, Mar. 2, 2009, Mobile Phone Based Clinical Microscopy for Global Health Application, demonstrated a proof of concept that, with an external optical configuration in front of the camera, a smartphone may function as a spectrometer.
However, wavelength accuracy of spectrometers must be calibrated in advance to establish the relation between the pixel number and the associated wavelength by means of a using a calibration lamp with known emission line wavelengths. In addition, a recalibration has to be performed periodically since the pixel number versus wavelength relation can change with ambient temperature variations, or disturbance to the optical configuration in front of the camera, or the variations of the auto-focusing lens position commonly occurs in smartphone. Given that this calibration procedure has to be performed off-line, it would be desirable to address the need for a smartphone-based optical spectrometer that has simultaneous self-referencing and spectrum measurement capabilities to achieve excellent wavelength reproducibility.
There is considerable prior art in the development and mechanism and operation of optical spectrometers, spectrophotometers, calorimeters, and the like devices for measuring the light wavelength that is reflected, transmitted or scattered from physical objects.
Among the proposed portable spectrometer solutions were:
In U.S. Pat. No. 6,043,893 (Trelman, Allan, et al.) discloses a manually portable spectrometer and method of detection of absorption and reflection of light.
In U.S. Pat. No. 7,019,833 B2 (Harnisch, Berad) discloses a miniature high resolution optical spectrometer.
In U.S. Pat. No. 7,199,876 B2 (Mitchell, Thomas) discloses a compact hyper spectral imager.
Among the proposed solutions for self-referencing spectrometers were:
In U.S. Pat. Application Publication No. 2008/0174768 A1 (Belz, Mathias) discloses A light emitting diode (LED) based detection system is employed for spectroscopy based application. LEDs are used as monochromatic light sources for applications at specific and pre-defined wavelengths.
In U.S. Pat. No. 6,774,368 B2 (Busch, Kenneth et al) discloses a dispersive, diffraction grating, NIR spectrometer that automatically calibrates the wavelength scale of the instrument without the need for external wavelength calibration materials.
Among the proposed solutions for portable spectrometer utilizing mobile computing devices were:
In U.S. Pat. No. 8,947,656 B2 to Cunningham discloses a mobile computing device that includes an image sensor to detect the result of a biomolecular assay that may be determined from the wavelength spectrum.
In U.S. Patent Application No. 2003/0136837 to Amon et al discloses a method and a system for security documents are authenticated through the methods of imaging, spectroscopy, etc.
In U.S. Patent Application No. 2006/0082760 to Lin discloses an optical sensing module to capture a group of images of a fingerprint on a finger of the user of the mobile phone.
In U.S. Patent Application No. 2006/0279732 to Wang et al discloses a spectroscopic sensor that is integrated with a mobile communication device that is capable of measuring optical spectra.
However, none of these prior art addresses the need for a low-cost optical spectrometer using the camera in a mobile computing device that simultaneously self-referencing and measure optical spectrum of physical object. It is therefore an aim of the present invention to provide a novel system that can simultaneously self-referencing and measure of spectral characteristics in real time with the use of software App for a mobile computing device to enhance the visual interpretation of the spectrum that will provide spectral wavelength information inexpensively.